U.S. patent application number 14/036463 was filed with the patent office on 2015-03-26 for rotor blade assembly with shim plate for mitigating pitch bearing loads.
This patent application is currently assigned to General Electric Company. The applicant listed for this patent is General Electric Company. Invention is credited to Eric Morgan Jacobsen, Adam Daniel Minadeo, Alexander William Vossler.
Application Number | 20150086359 14/036463 |
Document ID | / |
Family ID | 51542239 |
Filed Date | 2015-03-26 |
United States Patent
Application |
20150086359 |
Kind Code |
A1 |
Jacobsen; Eric Morgan ; et
al. |
March 26, 2015 |
ROTOR BLADE ASSEMBLY WITH SHIM PLATE FOR MITIGATING PITCH BEARING
LOADS
Abstract
The invention is directed to a rotor blade assembly for a wind
turbine designed to mitigate pitch bearing loads. The rotor blade
assembly includes a rotor blade, a pitch bearing, and at least one
shim plate. The rotor blade includes a body extending between a
blade root and a blade tip. The pitch bearing includes an outer
race, an inner race, and a plurality of roller elements between the
outer race and the inner race. As such, the inner race is rotatable
relative to the outer race. The at least one shim plate may be
configured between the inner race and the blade root or between the
outer race and a hub of the wind turbine so as to mitigate loads
experienced by the pitch bearing.
Inventors: |
Jacobsen; Eric Morgan;
(Greenville, SC) ; Minadeo; Adam Daniel;
(Greenville, SC) ; Vossler; Alexander William;
(Greenville, SC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
General Electric Company |
Schenectady |
NY |
US |
|
|
Assignee: |
General Electric Company
Schenectady
NY
|
Family ID: |
51542239 |
Appl. No.: |
14/036463 |
Filed: |
September 25, 2013 |
Current U.S.
Class: |
416/1 ;
416/174 |
Current CPC
Class: |
F03D 80/70 20160501;
F03D 1/0658 20130101; Y02E 10/721 20130101; Y02P 70/50 20151101;
Y02E 10/726 20130101; F05B 2250/292 20130101; F16C 2360/31
20130101; Y02P 70/523 20151101; F03D 1/0633 20130101; F05B 2260/79
20130101; F16C 19/08 20130101; Y02E 10/72 20130101; F16C 35/077
20130101; F05B 2230/80 20130101; Y02E 10/722 20130101 |
Class at
Publication: |
416/1 ;
416/174 |
International
Class: |
F03D 1/06 20060101
F03D001/06 |
Claims
1. A rotor blade assembly for a wind turbine, the rotor blade
assembly comprising: a rotor blade including a body extending
between a blade root and a blade tip; a pitch bearing comprising an
outer race, an inner race, and a plurality of roller elements
between the outer race and the inner race such that the inner race
is rotatable relative to the outer race, the inner race being
coupled to the blade root, the outer race configured to couple to a
hub of the wind turbine; and at least one shim plate configured
between the inner race and the blade root, wherein the shim plate
is configured to mitigate loads in the pitch bearing.
2. The rotor blade assembly of claim 1, wherein the inner race
comprises a top surface defining a radial dimension, the shim plate
having a width that is equal to or less than the radial
dimension.
3. The rotor blade assembly of claim 1, further comprising a
plurality of shim plates spaced circumferentially about the inner
race, the plurality of shim plates secured between the inner race
and the blade root.
4. The rotor blade assembly of claim 3, wherein at least one of the
shim plates is located on a pressure side of the pitch bearing
corresponding to a pressure side surface of the rotor blade and at
least one of the shim plates is located on a suction side of the
pitch bearing corresponding to a suction side surface of the rotor
blade.
5. The rotor blade assembly of claim 1, further comprising at least
one shim plate between the outer race and the hub.
6. The rotor blade assembly of claim 1, wherein the at least one
shim plate comprises a base and at least one tapered edge.
7. The rotor blade assembly of claim 1, wherein the at least one
shim plate comprises one or more through holes, each of the through
holes corresponding to one of a root bolt of the blade root or a
hub bolt of the hub, wherein the through holes are configured to
couple the shim plate between one of the inner race and the blade
root or the outer race and the hub.
8. The rotor blade assembly of claim 7, wherein the at least one
shim plate comprises one or more segments, each of the segments
comprising a slot, wherein the slots of each segment form the
through holes when the segments are connected.
9. The rotor blade assembly of claim 6, wherein the at least one
shim plate further comprises opposing tapered longitudinal
edges.
10. The rotor blade assembly of claim 1, wherein the at least one
shim plate further comprises a tapered radial edge.
11. The rotor blade assembly of claim 1, wherein the at least one
shim plate comprises a plurality of shim layers having varying
lengths.
12. The rotor blade assembly of claim 11, wherein the plurality of
shim layers are stacked atop each other such that the varying
lengths form opposing tapered edges having a step
configuration.
13. The rotor blade assembly of claim 1, wherein the at least one
shim plate is formed integrally with one of the blade root or the
pitch bearing.
14. A rotor blade assembly for a wind turbine, the rotor blade
assembly comprising: a rotor blade including a body extending
between a blade root and a blade tip; a pitch bearing comprising an
outer race, an inner race, and a plurality of roller elements
between the outer race and the inner race such that the inner race
is rotatable relative to the outer race, the outer race being
coupled to a hub of the wind turbine; and at least one shim plate
configured between the outer race and the hub, wherein the shim
plate is configured to mitigate loads in the pitch bearing.
15. The rotor blade assembly of claim 14, wherein the outer race
comprises a bottom surface defining a radial dimension, the shim
plate having a width that is equal to or less than the radial
dimension.
16. The rotor blade assembly of claim 14, wherein the shim plate
further comprises opposing tapered longitudinal edges.
17. The rotor blade assembly of claim 14, wherein the at least one
shim plate further comprises a tapered radial edge.
18. A method for mitigating loads in a pitch bearing of a wind
turbine, the method comprising: providing a rotor blade configured
to couple to a hub of a wind turbine via the pitch bearing, the
pitch bearing comprising and outer race and an inner race;
identifying at least one location on the pitch bearing experiencing
a loading; installing at least one shim plate at the identified
location; and, securing the rotor blade to the hub of the wind
turbine via the pitch bearing such that the shim plate mitigates
the loading in the pitch bearing during operation of the wind
turbine.
19. The method of claim 18, further comprising sizing the shim
plate to accommodate the loading.
20. The method of claim 18, wherein the loading is representative
of at least one of bearing ball contact stresses, blade root
resultant moments, or hard pressure spots.
Description
FIELD OF THE INVENTION
[0001] The present subject matter relates generally to wind
turbines and, more particularly, to a rotor blade assembly for a
wind turbine with one or more shim plates for mitigating pitch
bearing loading.
BACKGROUND OF THE INVENTION
[0002] Wind power is considered one of the cleanest, most
environmentally friendly energy sources presently available, and
wind turbines have gained increased attention in this regard. A
modern wind turbine typically includes a tower, generator, gearbox,
nacelle, and one or more rotor blades. The rotor blades capture
kinetic energy from wind using known airfoil principles and
transmit the kinetic energy through rotational energy to turn a
shaft coupling the rotor blades to a gearbox, or if a gearbox is
not used, directly to the generator. The generator then converts
the mechanical energy to electrical energy that may be deployed to
a utility grid.
[0003] To ensure that wind power remains a viable energy source,
efforts have been made to increase energy outputs by modifying the
size and capacity of wind turbines. One such modification has been
to increase the length of the rotor blades. However, as is
generally understood, the loading on a rotor blade is a function of
blade length, along with wind speed and turbine operating states.
Thus, longer rotor blades may be subject to increased loading,
particularly when a wind turbine is operating in high-speed wind
conditions.
[0004] During the operation of a wind turbine, the loads acting on
a rotor blade are transmitted through the blade and into the blade
root. Thereafter, the loads are transmitted through a pitch bearing
disposed at the interface between the rotor blade and the wind
turbine hub. Typically, the hub has a much higher stiffness than
the rotor blades. Thus, due to the stiffness differential between
the hub and the rotor blades, the pitch bearings are often
subjected to extreme, varying and/or opposing loads. For example,
the inner race of each pitch bearing (i.e., the portion typically
coupled to the rotor blades) may be subjected to varying, localized
loads resulting from flapwise or edgewise bending of the rotor
blades, whereas the outer race of each pitch bearing (i.e., the
portion typically coupled to the hub) may be subjected to lower
and/or differing loads. This variation in loading across the inner
and outer races can result in substantial damage to the pitch
bearings caused by high bearing contact stresses, high blade root
resultant moments, and hard pressure spots.
[0005] Various systems and methods have been employed to control
such varying loads in an effort to protect the pitch bearing. For
example, one method involves loosening the nuts on the bolts in
line with the hard pressure spots such that gaps are created when
the pitch bearing is overloaded. Such a method, however, tends to
overload adjacent bolts and is therefore not very effective.
[0006] Accordingly, an improved system and method for mitigating
loads in a pitch bearing, such as ball and raceway bearing contact
stresses, would be desired in the art. For example, a rotor blade
assembly having a shim plate configured to mitigate bearing contact
stresses would be advantageous.
BRIEF DESCRIPTION OF THE INVENTION
[0007] Aspects and advantages of the invention will be set forth in
part in the following description, or may be obvious from the
description, or may be learned through practice of the
invention.
[0008] In one aspect, the present subject matter is directed to a
rotor blade assembly for a wind turbine. The rotor blade assembly
includes a rotor blade, a pitch bearing, and at least one shim
plate. The rotor blade includes a body extending between a blade
root and a blade tip. The pitch bearing includes an outer race, an
inner race, and a plurality of roller elements between the outer
race and the inner race. As such, the inner race is rotatable
relative to the outer race. Further, the inner race is coupled to
the blade root. The at least one shim plate is configured between
the inner race and the blade root so as to mitigate loads in the
pitch bearing.
[0009] In another aspect a rotor blade assembly for a wind turbine
having a rotor blade, a pitch bearing, and at least one shim plate
is disclosed. The rotor blade includes a body extending between a
blade root and a blade tip. The pitch bearing includes an outer
race, an inner race, and a plurality of roller elements between the
outer race and the inner race such that the inner race is rotatable
relative to the outer race. Further, the outer race is coupled to a
hub of the wind turbine. The at least one shim plate is configured
between the outer race and the hub so as to mitigate loads in the
pitch bearing.
[0010] In still another aspect, a method for mitigating loads in a
pitch bearing of a wind turbine is disclosed. The method includes
providing a rotor blade configured to couple to a hub of a wind
turbine via the pitch bearing, the pitch bearing comprising and
outer race and an inner race; identifying at least one location on
the pitch bearing experiencing a loading; installing at least one
shim plate at the location; and, securing the rotor blade to the
hub of the wind turbine via the pitch bearing such that the at
least one shim plate mitigates the loading in the pitch bearing
during operation of the wind turbine.
[0011] These and other features, aspects and advantages of the
present invention will become better understood with reference to
the following description and appended claims. The accompanying
drawings, which are incorporated in and constitute a part of this
specification, illustrate embodiments of the invention and,
together with the description, serve to explain the principles of
the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] A full and enabling disclosure of the present invention,
including the best mode thereof, directed to one of ordinary skill
in the art, is set forth in the specification, which makes
reference to the appended figures, in which:
[0013] FIG. 1 illustrates a perspective view of one embodiment of a
wind turbine;
[0014] FIG. 2 illustrates a perspective view of one of the rotor
blades of the wind turbine shown in FIG. 1;
[0015] FIG. 3 illustrates a cross-sectional view of one embodiment
of the rotor blade assembly in accordance with aspects of the
present subject matter;
[0016] FIG. 4 illustrates an exploded view of one embodiment of a
rotor blade assembly according to the present disclosure;
[0017] FIG. 5 illustrates a perspective view of one embodiment of a
shim plate according to the present disclosure;
[0018] FIG. 6 illustrates a perspective view of another embodiment
of a shim plate according to the present disclosure;
[0019] FIG. 7 illustrates a top view of one embodiment of a shim
plate according to the present disclosure;
[0020] FIG. 8 illustrates a top view of another embodiment of a
shim plate according to the present disclosure;
[0021] FIG. 9 illustrates a side view of one embodiment of a shim
plate according to the present disclosure;
[0022] FIG. 10 illustrates a side view of another embodiment of a
shim plate according to the present disclosure;
[0023] FIG. 11 illustrates a side view of another embodiment of a
shim plate according to the present disclosure; and,
[0024] FIG. 12 illustrates a method for mitigating loads in a pitch
bearing of a wind turbine according to the present disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[0025] Reference now will be made in detail to embodiments of the
invention, one or more examples of which are illustrated in the
drawings. Each example is provided by way of explanation of the
invention, not limitation of the invention. In fact, it will be
apparent to those skilled in the art that various modifications and
variations can be made in the present invention without departing
from the scope or spirit of the invention. For instance, features
illustrated or described as part of one embodiment can be used with
another embodiment to yield a still further embodiment. Thus, it is
intended that the present invention covers such modifications and
variations as come within the scope of the appended claims and
their equivalents.
[0026] In general, the present subject matter is directed to a
rotor blade assembly for a wind turbine having at least one shim
plate configured between a rotor blade a hub to mitigate loads in a
pitch bearing, such as ball contact stresses. The shim plate is
generally a thin, optionally tapered or wedged piece of material,
used to fill a gap or space between a rotor blade and a hub of the
wind turbine. The shim plate(s) may also be integral with the rotor
blade, the hub, and/or the pitch bearing. The pitch bearing
generally includes an outer race, an inner race, and a plurality of
roller elements between the outer race and the inner race such that
the inner race is rotatable relative to the outer race. As such,
the at least one shim plate may be configured to fit between the
inner race and a blade root of the rotor blade or between the outer
race and a hub of the wind turbine so as to mitigate loads in the
pitch bearing.
[0027] Accordingly, the present subject matter as described herein
provides many technical and commercial advantages. For example, the
addition of one or more shim plates configured between a new or
existing rotor blade and a wind turbine hub can increase bearing
load capacity without substantially increasing installation and/or
maintenance costs. Further, retrofitting existing wind turbines
with one or more shim plates as disclosed herein does not require
the use of costly cranes.
[0028] Referring now to the drawings, FIG. 1 illustrates a side
view of one embodiment of a wind turbine 10 according to the
present disclosure. As shown, the wind turbine 10 generally
includes a tower 12, a nacelle 14 mounted on the tower 12, and a
rotor 16 coupled to the nacelle 14. The rotor 16 includes a
rotatable hub 18 and at least one rotor blade 20 coupled to and
extending outwardly from the hub 18. For example, in the
illustrated embodiment, the rotor 16 includes three rotor blades
20. However, in an alternative embodiment, the rotor 16 may include
more or less than three rotor blades 20. Each rotor blade 20 may be
spaced about the hub 18 to facilitate rotating the rotor 16 to
enable kinetic energy to be transferred from the wind into usable
mechanical energy, and subsequently, electrical energy. For
instance, the hub 18 may be rotatably coupled to an electric
generator (not shown) positioned within the nacelle 14 to permit
electrical energy to be produced.
[0029] Referring now to FIG. 2, a perspective view of one of the
rotor blades 20 shown in FIG. 1 is illustrated in accordance with
aspects of the present subject matter. As shown, the rotor blade 20
includes a blade root 22 configured for mounting the rotor blade 20
to the hub 18 of the wind turbine 10 (FIG. 1) and a blade tip 24
disposed opposite the blade root 22. A body 26 of the rotor blade
20 may extend lengthwise between the blade root 22 and the blade
tip 24 and may generally serve as the outer shell of the rotor
blade 20. As is generally understood, the body 26 may define an
aerodynamic profile (e.g., by defining an airfoil shaped
cross-section, such as a symmetrical or cambered airfoil-shaped
cross-section) to enable the rotor blade 20 to capture kinetic
energy from the wind using known aerodynamic principles. Thus, the
body 26 may generally include a pressure side 28 and a suction side
30 extending between a leading edge 32 and a trailing edge 34.
Additionally, the rotor blade 20 may have a span 36 defining the
total length of the body 26 between the blade root 22 and the blade
tip 24 and a chord 38 defining the total length of the body 26
between the leading edge 32 and the trailing edge 34. As is
generally understood, the chord 38 may vary in length with respect
to the span 26 as the body 26 extends from the blade root 22 to the
blade tip 24.
[0030] Moreover, as shown, the rotor blade 20 may also include a
plurality of T-bolts or root attachment assemblies 40 for coupling
the blade root 20 to the hub 18 of the wind turbine 10. In general,
each root attachment assembly 40 may include a barrel nut 42
mounted within a portion of the blade root 22 and a root bolt 44
coupled to and extending from the barrel nut 42 so as to project
outwardly from a root end 46 of the blade root 22. Alternatively,
the barrel nut 42 may be eliminated from the root attachment
assembly 40. For example, each of the root attachment assemblies 40
may simply include a threaded root bolt 44 projecting outwardly
from the root end 46 of the blade root 22. By projecting outwardly
from the root end 46, the root bolts 44 may generally be used to
couple the blade root 22 to the hub 18 (e.g., via a pitch bearing
50 (FIG. 3)), as will be described in greater detail below.
[0031] Referring now to FIGS. 3 and 4, several views of a rotor
blade assembly 50 having shim plate 100 for mitigating loads in a
pitch bearing 52 are illustrated in accordance with aspects of the
present subject matter. Specifically, FIG. 3 illustrates a
cross-sectional view of the rotor blade assembly 50 having a
plurality of shim plates 100 installed between the rotor blade 20
and the hub 18. Similarly, FIG. 4 illustrates an exploded view of
the rotor blade assembly 50 according to the present
disclosure.
[0032] As shown, the rotor blade assembly 50 includes the rotor
blade 20 coupled to the hub 18 via the pitch bearing 52. The pitch
bearing 52 includes an outer bearing race 54, an inner bearing race
56, and a plurality of roller elements (e.g., balls 58) disposed
between the outer and inner races 54, 56. The outer race 54 is
generally configured to be mounted to the hub 18 using a plurality
of hub bolts 62 and/or other suitable fastening mechanisms.
Similarly, the inner race 56 is generally configured to be mounted
to the blade root 22 of the rotor blade 20 using root bolts 44. For
example, as particularly shown in FIG. 3, the root bolt(s) 44
extend between a first end 64 and a second end 66. The first end 64
of each root bolt 44 may be configured to be coupled to a portion
of the inner race 56, such as by coupling the first end 64 to the
inner bearing race 56 using an attachment nut 68 and/or other
suitable fastening mechanism. The second end 66 of each root bolt
44 may be configured to be coupled to the blade root 22 via a
barrel nut 42.
[0033] As is generally understood, the inner race 56 may be
configured to be rotated relative to the outer race 54 (via the
roller elements 58) to allow the pitch angle of each rotor blade 20
to be adjusted. As shown in FIG. 3, such relative rotation of the
outer and inner races 54, 56 may be achieved using a pitch
adjustment mechanism 72 mounted within a portion of the hub 18. In
general, the pitch adjustment mechanism 72 may include any suitable
components and may have any suitable configuration that allows the
mechanism 72 to function as described herein. For example, as shown
in the illustrated embodiment, the pitch adjustment mechanism 72
may include a pitch drive motor 74 (e.g., an electric motor), a
pitch drive gearbox 76, and a pitch drive pinion 78. In such an
embodiment, the pitch drive motor 74 may be coupled to the pitch
drive gearbox 76 so that the motor 74 imparts mechanical force to
the gearbox 76. Similarly, the gearbox 76 may be coupled to the
pitch drive pinion 78 for rotation therewith. The pinion 78 may, in
turn, be in rotational engagement with the inner race 56. For
example, as shown in FIGS. 3 and 4, a plurality of gear teeth 80
may be formed along an inner circumference 86 of the inner race 56,
with the gear teeth 80 being configured to mesh with corresponding
gear teeth 82 formed on the pinion 78. Thus, due to meshing of the
gear teeth 80, 82, rotation of the pitch drive pinion 78 results in
rotation of the inner race 56 relative to the outer race 54 and,
thus, rotation of the rotor blade 20 relative to the hub 18.
[0034] Referring now to FIG. 4, an exploded view of the rotor blade
assembly 50 according to the present disclosure is illustrated. As
shown in the illustrated embodiment, three shim plates 100 are
spaced apart circumferentially about the inner race 56 of the pitch
bearing 52. As such, the shim plates 100 may be configured between
a top surface 88 of the inner race 56 and the blade root 22. More
specifically, at least one of the shim plates 100 is located
approximate to a pressure side of the pitch bearing 52
corresponding to the pressure side surface 28 of the rotor blade
20, whereas two shim plates 100 are located approximate to a
suction side of the pitch bearing 52 corresponding to the suction
side surface 30 of the rotor blade 20. Additionally, one or more
shim plates 100 may be spaced circumferentially about the outer
race 54 of the pitch bearing 52 and between the outer race 54 and
the hub 18. For example, as illustrated, one shim plate 100 is
located between the outer race 54 and the hub 18. More
specifically, the shim plate 100 is configured between a bottom
surface 92 of the outer race 54 and the hub 18.
[0035] It should be understood that the rotor blade assembly 50 may
include any number of shim plates 100 and the shim plates 100 may
be arranged at any location along the circumference of the pitch
bearing 52 and between either the inner race and the blade root or
the outer race and the hub. As such, the shim plates 100 can be
located at any location on the pitch bearing 52 experiencing uneven
loading, such as, for example, corresponding to a hard pressure
spot.
[0036] In another embodiment, the top surface 88 of the inner race
56 defines a radial dimension R.sub.1 (FIG. 4), whereas and the
shim plate 100 defines a width W (FIG. 5) that is equal to or less
than the radial dimension R.sub.1. As such, in various embodiments,
the shim plate 100 fits within the radial dimension R.sub.1 of the
inner race 56 and does not extend within the open area within the
inner race 56. Additionally, in such an embodiment, the width W of
the shim plate 100 does not interfere with the outer race 54 when
the shim plate 100 is configured between the inner race 56 and the
blade root 22. Similarly, the bottom surface 92 of the outer race
54 defines a radial dimension R.sub.2 such that the width W of the
shim plate 100 is equal to or less than the radial dimension
R.sub.2. As such, in various embodiments, the shim plate 100 fits
within the radial dimension R.sub.2 of the outer race 54 and does
not interfere with the inner race 56 when the shim plate 100 is
configured between the outer race 54 and the hub 18.
[0037] Referring now to FIG. 5-11, various detailed embodiments of
the shim plate according to the present disclosure are illustrated.
For instance, FIGS. 5 and 6 illustrates close-up perspective views
of various embodiments of the shim plate according to the present
disclosure, whereas FIGS. 7-11 illustrate top and side views of
further embodiments of the shim plate according to the present
disclosure. As shown specifically in FIGS. 5-8 the shim plate 100,
150, 200 has a base 102, 152, 202 and at least one tapered edge
104, 154, 204. Additionally, as shown particularly in FIG. 5, the
base 102 may have a substantially rectangular cross-section as
indicated by section A-A. As such, the base 102 has substantially
linear radial edges 110. In an alternative embodiment, as shown in
FIG. 6, the base 202 may have a substantially tapered cross-section
as indicated by section B-B. As such, the base 102 has at least one
substantially tapered radial edge 210. Accordingly, the shim plate
200 may include a tapered radial edge 210 across the full shim
width W or across only a portion of the shim width W.
[0038] As shown in FIG. 9, the base 102 has a height H (or
thickness) and a total length L.sub.1. The total length L.sub.1 may
be any suitable length and typically ranges from about 200
millimeters (mm) to about 3 meters (m). The height H may be any
suitable height and/or thickness and typically ranges from about
0.5 mm to about 10 mm, such as, for example, 0.7 mm. Further, the
base 102 may have any suitable shape so as to fit in the desired
locations as described herein. For example, as shown in FIGS. 5-7,
the base 102 has a typically arcuate shape so as to correspond with
the shape of the inner 56 and outer 54 races of the pitch bearing
52. In alternative embodiments, the base 102, 152 may have a
rectangular, square, triangular, circular, or similar shape. For
example, as shown in FIG. 8, the base 152 has a rectangular
shape.
[0039] The tapered edge(s) 104, 154, 204 are provided to allow
intimate contact at all bearing perimeter locations with a finite
in-plane shear stress in the blade shell. Further, the tapered
edge(s) 104, 154, 204 minimize added friction that may exist due to
rotation of the inner 56 and outer 54 bearing races. It should be
understand that the term "tapered edges" is meant to encompass at
least a tapered-sloped edge, as well as a tapered-stepped edge, as
will be discussed in more detail herein. As shown in the
embodiments of FIGS. 5 and 9, the shim plate 100 may include
opposing tapered edges 104 having corresponding slopes. For
example, as depicted in the embodiment of FIG. 9, the slope of each
of the tapered edges 104 is equal to L.sub.2/H and L.sub.3/H,
respectively. The lengths L.sub.2, L.sub.3 of the tapered edges 104
may be any suitable length and typically ranges from about 250 mm
to about 750 mm, such as, for example, 500 mm. As mentioned, the
height H may be any suitable height and typically ranges from about
0.2 mm to about 10 mm, such as, for example, 0.7 mm. As such, the
corresponding slopes of the tapering edges ranges from about
0.00026 to about 0.04, such, for example, 0.0014. Further, the
slopes of the tapering edges 104 may be any appropriate slope to
provide appropriate contact between the rotor blade 20 and the
pitch bearing 52 and/or the hub 18 and the pitch bearing 52.
[0040] Alternatively, as shown in FIGS. 10 and 11, the shim plates
300, 400 may include opposing tapered edges 304, 404 having a step
configuration. More specifically, as shown in FIG. 10, the shim
plate 300 may include multiple shim layers 308 having varying
lengths and stacked atop one another until a suitable height H or
thickness is obtained. It should be understood that the shim plates
100, 200, 300, 400 described herein may include any number of shim
layers 108, 308, 408 from one to greater than one. For example, as
shown in FIG. 10, the illustrated embodiment includes two shim
layers 308, whereas the shim plate 400 of FIG. 11 includes four
shim layers 408. In addition, each of the shim layers 308, 408 has
a varying length such that the varying lengths (e.g. L.sub.4 and
L.sub.5) form the opposing tapered edges 304, 404 having a step
configuration.
[0041] Further, the opposing tapered edges 104, 204, 304, 404 may
be identical to one another or may vary according to any of the
embodiments described herein. For example, in one embodiment, one
of the edges may have a tapered-sloped configuration (as shown in
FIG. 9), whereas the opposing edge may have a step configuration
(as shown in FIGS. 10 and 11). In another embodiment, both edges
may have a tapered-sloped configuration; however, the slopes may
vary.
[0042] Referring back to FIG. 5, the shim plate 100 may include one
or more through holes 106 for coupling the shim plate 100 between
the inner race 56 and the blade root 22 or between the outer race
54 and the hub 18. As such, the through holes 106 of the shim plate
100 may correspond to the root bolts 44 of the blade root 22 or the
hub bolts 62 of the hub 18. In an additional embodiment, as shown
in FIG. 8, the shim plate 150 may include one or more segments 158,
wherein each segment 158 has at least one slot 160. The segments
158 may be inner and outer interlocking segments for inserting the
shim plate 150 around corresponding bolts 44, 62. As such, the
slots 160 of the segments 158 may form the through holes 156 when
the segments 158 are connected, i.e. inserted around a blade bolt
or a hub bolt. In alternate embodiments, the shim plate 100 may be
secured between the inner race 56 and the blade root 22 or between
the outer race 54 and the hub 18 using any other suitable means,
such as adhesives or friction.
[0043] It should also be understood that the shim plate(s)
described herein may be constructed of any suitable materials so as
to mitigate loads experienced by the pitch bearing. In one
embodiment, it is desirable for the joint of the material to be as
stiff as possible. As such, in various embodiments, the shim
plate(s) may be constructed of metal, such as steel or similar. In
a further embodiment, the shim plate may be constructed of a
composite material, such as a fiberglass laminate, similar to the
rotor blade.
[0044] Referring now to FIG. 12, one embodiment of a method 500 for
mitigating loads in a pitch bearing of a wind turbine according to
the present disclosure is illustrated. The method 500 includes a
step 502 of providing a rotor blade configured to couple to a hub
of a wind turbine via the pitch bearing. The method 500 includes
identifying at least one location on the pitch bearing experiencing
a loading (step 504) and then installing at least one shim plate at
the identified location (step 506). The method 500 then includes
securing the rotor blade to the hub of the wind turbine via the
pitch bearing such that the at least one shim plate mitigates the
loading in the pitch bearing during operation of the wind turbine
(step 508).
[0045] In one embodiment, the step 504 of identifying at least one
location on the pitch bearing experiencing a loading further
includes identifying a spar cap in the rotor blade. As such, one or
more shim plates can be placed in-line with the spar cap. In
another embodiment, one or more shim plates can be inserted on a
pressure side surface of the rotor blade in-line with the spar cap,
whereas one or more shim plates can be inserted on the suction side
surface of the rotor blade adjacent to the spar cap. In another
embodiment, the step of installing at least one shim plate at the
identified location further includes installing at least one shim
plate between the rotor blade and the hub and spacing a plurality
of shim plates circumferentially about the pitch bearing. In
addition, the method 500 may include sizing the shim plate to
accommodate the loading. In various embodiments, the loading may be
representative of bearing ball contact stresses, blade root
resultant moments, hard pressure spots or similar.
[0046] The step 506 of installing the at least one shim plate at
the identified location may completed using a variety of
techniques. For example, in one embodiment, where the rotor blade
is being retrofitted uptower with the one or more shim plates, the
method may include positioning the rotor blade in a six o'clock
position relative to the hub, loosening one or more blade bolts
until a gap opens between the rotor blade and the hub, inserting
the at least one shim plate over one of the blade bolts, and
tightening the blade bolts such that the at least one shim plate is
secured between the rotor blade and the hub so as to mitigate loads
in the pitch bearing. In another embodiment, one or more shim
plates may be screwed into an end face of the pitch bearing, such
as a top or bottom surface of the pitch bearing. In still an
additional embodiment, where one or more shim plates are configured
in multiple segments each having a slot, the segments may be
inserted around the blade bolts or hub bolts via corresponding
slots and then secured between the rotor blade and the hub. In yet
another embodiment, one or more shim plates may be inserted over
root bolts 44 before the rotor blade is coupled to the hub via the
pitch bearing. Additionally, one or more shim plates may be
inserted over the hub bolts 62. In another embodiment, the method
500 may include removing one or more of the blade bolts, installing
one or more of the shim plates in the location(s) of the
corresponding removed blade bolts, and then replacing the blade
bolts.
[0047] The method 500 as described herein may also include
machining the pitch bearing so as to provide one or more shim
plates or protrusions integral with the pitch bearing, such as on
the top or bottom surfaces of the pitch bearing. In another
embodiment, the method may include machining the hub or the rotor
blade such that one or more shim plates or protrusions are provided
in an end face of the hub or the rotor blade. As such, the non-flat
mating surfaces between the pitch bearing and the rotor blade
and/or the pitch bearing and the hub mitigates loads in the pitch
bearing.
[0048] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they include structural elements that do not
differ from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal languages of the claims.
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